Todd Mullins and his wife, Julie, started going to a shopping center 15 minutes from their Palm Beach Gardens, Fla., home about a year ago—after they joined a gym inside of it. They work out at the Orangetheory Fitness there three to four times a week, and at least half the time visit a nearby juice shop, restaurant or Trader Joe’s, he says.

“There would be no other reason to go to that mall,” says Mr. Mullins, a senior pastor at a local church.